search_messages

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The annotations (readOnlyHint=true, destructiveHint=false) already signal a safe read operation, and the description adds materially useful behavioral context beyond them: the literal handling of `%` and `_`, the attributedBody gap, and the hard 200-row limit on `limit`. The security advisory about treating message text as data rather than instructions is an exemplary disclosure for an LLM-driven agent. No contradiction with the safe-read annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Five sentences, three short paragraphs, and every clause pulls its weight. Purpose, matching rules, known coverage limitation, limit cap, and a security note — all under 70 words. The structure front-loads the core definition and parcels out caveats in decreasing importance. The final warning about prompt injection is a distinctive, high-value addition.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a read-only search tool with an output schema, this description is thorough: it documents the matching algorithm, data availability, and edge-case limitations, and even warns about hostile content. One minor gap is that it never addresses case-sensitivity or namespace/regex behavior, which could plausibly matter when using a search. But given the presence of annotations and output schema, coverage is strong overall.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 0% schema description coverage, the description carries the full burden for parameter documentation. It compensates partially by explaining the `limit` cap and the literal-match semantics of the query string, but it doesn't add much beyond what the parameter names alone suggest for a 2-parameter tool. The value it does add (wildcard literalness, cap) is meaningful, but the semantic depth is still minimal and some behavior (e.g., case sensitivity) remains unspecified.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a crisp, specific statement: 'Substring search over message bodies.' This clearly establishes verb (search) and resource (message bodies) and distinguishes it from sibling tools like get_messages and get_recent_messages. Subsequent sentences add behavioral specificity (plain text column, literal wildcards) without ambiguity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides clear contextual guidance about when the tool is effective versus when it falls short ('Some newer messages store their body only in attributedBody and will not be found by this search'), which implicitly tells the agent when to consider alternatives like get_messages. However, it never explicitly names sibling alternatives or says 'use X instead,' so it stops short of a 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.